The present invention is directed towards an apparatus and methods for utilizing energy by employing gas concentration cells. Particularly, this invention is directed toward the conversion of heat energy directly into electrical energy by the use of gas concentration cells and using electrical energy to pump heat energy with gas concentration cells.
The rising costs of conventional energy sources such as gas, coal and oil have led to research in alternative energy sources and methods to increase conversion efficiencies of energy sources in general. Solar energy and tidal energy are two examples of alternative energy sources which have been explored. But, the energy conversion costs, related to these alternative energy sources, remains high and as of yet, widespread commercial application has not occurred.
Some research on the use of gas concentration cells and metal hydrides to convert heat, including solar heat, into electricity has been carried out.
The gas concentration cell operates on principles similar to other reversible electrochemical cells. The gas cell has two electrodes, made of like materials, and an electrolyte. The gas cell is capable of generating electricity when a differential gas pressure is applied across the cell. For example, a high pressure gas is applied at a face of the first electrode and a low pressure gas is applied to a second electrode at a face away from the first electrode. The gas, traveling from high pressure to low pressure, permeates the first electrode where it ionizes. The protons so formed diffuse through the electrolyte and reform as hydrogen at the second electrode.
A gas concentration cell produces a voltage, under conditions of negligible load, which is given by the Nernst equation: ##EQU1## Where, E is the voltage; R is the universal gas constant; T is the absolute temperature; F is the Faraday constant, and n is the number of electrons given up or received per molecule reacted. P.sub.H and P.sub.L are the high and low pressures, respectively.
Prior research, in the area of gas concentration cells and solar energy conversion, was directed toward the use of metal hydrides, as the means of storing and supplying gas to the concentration cells. The metal hydrides are capable of absorbing gas. The gas is released from the hydride when heated. It was believed that a solar energy conversion apparatus could be constructed using a gas concentration cell as the electrical generator; two containers filled with metal hydride, one on each side of the cell to supply gas for pressurization, and the sun to supply solar energy, in the form of heat. The first container, filled with metal hydride, was saturated with gas and the second container having little or no absorbed gas. The first container was heated, gas was released creating a high pressure in the first container and the second container provided the low pressure side for the cell. Electricity was generated according to the Nernst equation. The gas permeated the cell and was absorbed by the hydride in the second container. When all the gas had been driven from the first container and collected in the second container, heat was applied to the second container and the process was reversed.
But, this energy conversion scheme was found to be flawed. Particularly, the flaws involved the use of the metal hydrides. The hydrides were found to be sensitive to the presence of contaminants in the gas. The most promising cell, from an economic point of view, required a significant amount of humidification. In other words, the water vapor needed for optimum cell operation would poison the hydride. The hydride was also found to lose the ability to store hydrogen after repeated cycling. Thus, the hydride could only be used for a finite number of cycles. The expense of the hydrides posed an economic problem. The metals, choosen from the rare earth group, were expensive. Additionally, large quantities of the metal hydrides were needed to store sufficient amounts of gas to make the process economically feasible. Thus, a solar energy conversion scheme using metal hydrides appeared commercially impracticable because of contamination problems, the finite number of cycles possible before hydride decomposition, the expense of the hydrides and the need to alternate the site of heat input.
An additional problem with energy conversion schemes are conversion inefficiencies. Conventional energy conversion schemes rely on machines with moving parts. For example, in the conversion of steam to electricity a turbine and generator are needed. The moving parts of those machines add energy losses to the conversion of energy from the form of heat to electrical energy. Thus, the cost of converting energy is increased due to the inefficencies of the conversion process.